Advisories

WDPN31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15E (NOLO) WARNING NR 062//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.7N 173.0E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 522 NM NORTHEAST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 44 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED VISIBLE SATELLITE IMAGERY DEPICTS TIGHTLY CURVED BANDING
WRAPPING INTO A WELL-DEFINED, ROUGHLY 22 NM DIAMETER EYE. THE
IMPROVING SYMMETRY OF THE COMPACT CENTRAL DENSE OVERCAST AND
COOLING CONVECTIVE CLOUD TOPS MARK AN IMPROVING TREND OVER THE PAST
SIX HOURS. THIS IMPROVEMENT CAN ALSO BE SEEN OVER A PAIR OF
SUCCESSIVE SSMIS 91 GHZ PASSES, WITH THE LATEST AT 051930Z
REVEALING A SOLID INNER CONVECTIVE CORE SURROUNDING A MICROWAVE
EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
MULTI-AGENCY EYE FIXES, INCLUDING THE SSMIS FIX DATA. THE INITIAL
INTENSITY WAS HELD AT 105 KNOTS AS THE RANGE OF SUBJECTIVE DVORAK
CURRENT INTENSITY ESTIMATES FELL SLIGHTLY (T5.0 TO T5.5) WHILE
RECENT OBJECTIVE ESTIMATES RANGE FROM ABOUT 102 TO 112 KNOTS. THE
ENVIRONMENT IS NOW ASSESSED AS FAVORABLE, WITH MODERATE POLEWARD
OUTFLOW, WARM 28-29 DEGREE CELSIUS WATERS, AND CIMSS ESTIMATED
VERTICAL WIND SHEAR OF 15 KNOTS (LOW), BEING OFFSET BY THE PRESENCE
OF DRY MID-LEVEL AIR SURROUNDING THE SYSTEM.

INITIAL WIND RADII BASIS: PARTIAL SCATTEROMETER DATA AND
PERSISTENCE

CURRENT STEERING MECHANISM: THE AXIS OF A DEEP-LAYER SUBTROPICAL
RIDGE (STR) TO THE NORTH


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.0 - 90 KTS
   PHFO: T5.5 - 102 KTS
   CIMSS ADT: 107 KTS AT 052330Z
   CIMSS AIDT: 112 KTS AT 052100Z
   CIMSS D-MINT: 107 KTS AT 052259Z
   CIMSS D-PRINT: 114 KTS AT 060140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TY 15E IS FORECAST TO CONTINUE TRACKING
GENERALLY WESTWARD TO WEST-NORTHWESTWARD WHILE IT REMAINS ON THE
SOUTHERN PERIPHERY OF THE STRONG STEERING SUB-TROPICAL RIDGE (STR)
DURING THE FIRST 60 HOURS OF THE FORECAST. AFTER TAU 60, A WEAKNESS
IS EXPECTED TO DEVELOP ALONG THE WESTERN PERIPHERY OF THE STR,
ALLOWING FOR A POLEWARD TURN INTO THE BREAK BETWEEN THE STR AND A
BUILDING LOW- TO MID-LAYER RIDGE CENTERED OVER JAPAN. FORWARD SPEEDS
ARE EXPECTED TO SLOW DURING THIS PERIOD DUE TO COMPETING STEERING
INFLUENCES AND LACK OF A DYNAMIC TROUGH TO AID IN RECURVATURE. A
WEAKENING TREND IS EXPECTED THROUGH TAU 60 AS A RIBBON OF 200 MB FLOW
BRANCHING OFF THE MID-LATITUDE JET IMPARTS INCREASING NORTHERLY VWS,
WHILE ENVIRONMENTAL MOISTURE IS EXPECTED TO REMAIN CONSTRAINED. AFTER
TAU 60, NOLO WILL BE IN A MORE FAVORABLE POSITION WITH THE JET TO
PROVIDE ADDITIONAL OUTFLOW FOR SLIGHT REINTENSIFICATION, AS SST
VALUES WILL REMAIN SUPPORTIVE.  


MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH
TAU 36, AFTER WHICH THE CROSS-TRACK SPREAD INCREASES THROUGHOUT THE
FORECAST PERIOD. BY THE 72 HOUR FORECAST POINT, MOST MODEL
SOLUTIONS INDICATE THE POLEWARD TURN, WITH HAFS AND ECMWF BEING
NOTABLE SOUTHERLY OUTLIERS PERSISTING A MORE WESTWARD TRACK. THE
JAPANESE MODELS LIE ALONG THE OPPOSITE END OF THE ENVELOPE,
DEPICTING A TIGHT RECURVATURE. THE MULTI-MODEL CONSENSUS AND AI
CONSENSUS LIE IN BETWEEN THESE TWO EXTREMES, WITH SPREAD BETWEEN
THE TWO GROUPINGS OF ABOUT 125 NM, WITH AI FAVORING A FASTER
RECURVE. THE SPREAD BETWEEN THESE TWO CONSENSUS METHODOLOGIES IS
NEARLY IDENTICAL AT THE 120 HOUR FORECAST POINT, DESPITE THE VERY
LARGE OVERALL MODEL SPREAD. THE JTWC TRACK WAS PLACED VERY CLOSE TO
THE PRIOR FORECAST, IN BETWEEN THE TWO GROUPS WITH MEDIUM
CONFIDENCE FROM TAU 0-72, AND LOW CONFIDENCE IN THE EXTENDED RANGE.
INTENSITY WISE, MOST AIDS AGREE ON A WEAKENING TREND THROUGH TAU
60, WITH HAFS BEING THE NOTABLE OUTLIER. THE JTWC INTENSITY
FORECAST LIES CLOSE TO THE PREVIOUS FORECAST, LARGELY DISCOUNTING
THE HAFS SOLUTION DUE TO THAT MODELS MORE SOUTHERLY TRACK BEING
LESS REPRESENTATIVE OF THE EXPECTED ENVIRONMENTAL CONDITIONS. GIVEN
THE LARGE TRACK SPREAD AND THE CORRELATION TO INTENSITY, OVERALL
FORECAST INTENSITY CONFIDENCE IS LOW IN BOTH PERIODS.


FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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